The California Air Resources Board has approved changes that give heavy-duty diesel engine manufacturers more time to comply with “technology forcing” regulations that require advances to engine onboard diagnostics systems that monitor nitrogen oxide emissions levels and particulate matter filter and sensor malfunctions.
But several engine makers told the board late last month that even the adjusted timelines to diesel monitoring emission malfunction thresholds during the 2013-2015 model years will still be difficult to meet, increasing the odds that OBD performance could fall short of expectations.
The manufacturers said that even the adjusted state requirements are still more stringent than those set by the U.S. Environmental Protection Agency.
“The OBD regulations are highly technical and complex, and they present challenges that test the limits of manufacturers’ design capability and resources,” Lisa Stegink, an attorney representing the Truck and Engine Manufacturers Association, told CARB board members. “We’re pleased to say that we have worked out many of the issues, but other issues remain.”
Engine maker Cummins Inc. executive Mark Stepper said the loosened requirements “do little more, if anything, towards developing the technology, but add risks for manufacturers and their customers.”
But CARB officials disagree with manufacturers about the extent of relaxation needed. They stuck to their plan to further ease the timeline, but said it was necessary to keep the pressure on engine manufacturers to develop better monitoring systems.
“While CARB’s staff believes these thresholds are technically feasible to meet, staff agrees some relaxation is necessary for the near-term model years, though it disagrees with manufacturers about the extent of the relaxation needed,” CARB said.
CARB Chairman Mary Nichols said the OBD systems are “an integral piece of the overall emissions standards.”
“Our OBD program is important because it ensures that vehicles and engines meet those standards in real world use and remain clean their entire life, not just when a vehicle is being certified,” Nichols said.
